Process of separating ores



Sept 22, 1942. A, WJRIALSTQN ETAL 2,296,368

PROCESS OF SEPARATING ORES l l Filed Nov. 24, 1939 2 Sheets-Sheet l ,AMINE FILM nl "I "Ilm WATER AMINE FILM coN'rmNlNe SIMCA VESSEL .32M wm A. W. RALSTON ETAL PROCESS OF SEPARATING ORES sept. 22,1942.

2= Sheets-Sheet 2 Filed Nov. 24, 1939 slow-rising, small bubbles mineral particles.

lseparated from the sangue 'Patented sept. 22, `1942 2,296,368 l PROCESS OF SEPARATING ORES Anderson W. Ralston and Ervin W. Segebrecht, Chicago, lll., assignorsv to Armour and Company, Chicago,

Ill., a corporation of Illinois Application November 24, 1939, Serial No. 306,024

12 Claims.

This invention relates to processes of separating silica from ores containing the same, and it comprises processes wherein a silica-containing ore which` is wetted with Water is brought into contact with'a film of a high molecular weight primary aliphatic amine floating on a water layer, the wetted ore passing from the water layer to and through the amine layer whereby the silica particles in said ore preferentially adsorb the amine, and the amine film then reformed on a` water layer whereby Athe silica particles in the ore are retained by the film 'and the other ore values passed through the film and under the water surface, thus bringing about a separation of the silica fr om the other ore particles, and then separately recovering the silica andthe other ore particles.

In the froth flotation separation of .ores it is 4 in question. In the flotation separationfof phos Av phate ore soaps, such as sodium oleate, are often are washed away and collected and others passover the table and are collected separately. The particular type of separation employed depends quite largely upon the nature of the ore itself;

however,froth flotation is the process most gen'- n erally employed. i

In froth otation the agents used may be either added directly to the cell or mixed with the concentrated pulp and the mixture then added to the cell. As stated before, various agents have been used as collectors depending upon the ore used. Gaudin (page 371) gives some typical separations of calcium phosphate from silica by the use of soaps. These examples are as follows:

- (1) an ore assaying 48.5% B. P. L. (bone phoscustomary to place the ore as an aqueous slurry in a flotation cell along with a flotation agent. The slurry is agitated in such a manner that air is drawn under the water surface. The flotation agent is specifically adsorbed by portions of the ore; air bubbles then attach themselves -to these portions and they float away from the remainder o1' the ore. Flotation" Gaudin writes upon froth flotation as follows: It has already been indicated that froth flotation is essentially a creaming process whereby the light air bubbles with or without attached mineral particles segregate from the heavier pulp. In agitation-type machines the units involved in this crcaming are relatively heavily loaded with Because 0f this characteristic mineralization the bubble-mineral aggregates are rigid, and since they reach the top of the pulp at low speed they do not entrain with them much pulp.l In pneumatic-type machines the units involved in the creaming are relatively fast-rising, large, lightly loaded bubbles which on account of v bonate.

On page 107 of his book entitled phate of lime) and containing 37.4% insolubles was treated with 1.6 lbs. per ton of oleic acid, 0.8 lb. per ton of crude pine oil, 0.6 1b. per ton of steam distilled pine oil, 0.25 1b. per ton of scrdium silicate and 0.2 1b. per ton of sodium car- 'I'he concentrate represented 54.6% of the original and assayed 75.1% B. P. L. and 4.3% acid insolubles. This corresponds to a phosphate recovery of 84.6% and a selectivity index of 9.1. (2) a lower grade ore which assayed 33.5% B. P. L. was treated with the same reagent. 'I'his gave a concentrate corresponding to 22.4% of the original and a middling which corresponded to 22.3%. 'I'he percentage B. P. L. of `the concentrate was 71.8 and of the middling 57.7 and they contained 1.9% acid insolubles respectively. This corresponds to a recovery of 47.9% of the original phosphate in the concentrate' and 38.4% in the middling. The tailings which represented 55.3% of the original sample contained 8.3%

their abundanceentrain in the bubble column a` as "per se means of separating the ore values.

Separations depending upon differences in specific gravity of the various ore values are sometimes conveniently employed. At other times the Y ore. is passed over tables and washed with running Water in such a manner that certain values B. P. L. and 89.2% acid insolubles.

Recently Lenher, U. S. Patent 2,132,002, has described a series of flotation agents containing positively charged ions. These agents are useful for the `froth flotation of certain ores. The salts of high molecular weight amines such as dodecyl or octadecyl' amine acetates or hydrochlorides fall in this class. In the Ralston and Pool application, Serial No. 221,008, it has been shown that the unionized amine molecule is superior to an ized amine molecule by of certain ores, particularly phosphate ores. In these cases the calcium phosphate is floated away A amine ion for `the froth flotation of ores. The

.flotation processes in this case are not dependent `upon the presence of positively charged lons, but

are due to the specinc adsorption of the unioncertain portions of the ore. l l

As above stated. fatty acids and their soaps are now extensively used for the froth flotation from the siliceous gangue. With the amines the lreverse is true and the' silica is floated leaving the calcium phosphate behind as the tailing.

`devise a process by which Quite excellent separations Aare possible by the use of the latter reagents, but from an economic standpoint it is necessary that such separations be decidedly' superior either as regards the separations obtained or the amount of reagent required before their large scale use is indicated. This is due to the fact that the amines or' amine salts are ,and probably always will be somewhat more expensive than the acids because the acids are the starting materials for the preparation of the amines. We have realized this phase of the problem and, consequently, have set ourselves to substantially smaller amounts of the amines can be used to effect a satisfactory separation As a consequence ofthis .study we have devised a process of separation which operates effectively with from one t ten percent of the amount of regaent required for a froth flotation.

We have discovered that if a layer of nely ground ore is passed up through a film of a high molecular weight amine forming a hn on a water surface in such a manner that the lm is disrupted and if this process is repeated by passing the ore layer down through the water surface the iilm is reformed and the silica present in the ore is retained in the nlm and the other ore values pass through the film and under the water surface. This process can be repeated the desired number of times until an essentially complete separation of one ore value from another is obtained. We have found that by this process ores containing silica as one of the components can be separated by the use of astonishingly small amounts of amines. In some cases the amount required is only one percent of that necessary to bring about the'equivalent separation by a froth flotation or by other methods. In the practice of this invention it is necessary to first eitl: er ele- Avate the ore layer through the amine lm, or

lower the water surface carrying the film in such a manner that the ore first comes in contact with the hydrophylic portion of the amine. Agitation of the water or the film is not desirable since if agitated the ability of the film to hold up the silica particles is materially reduced.

In order to operate this procedure we have deviscd and operated methods by which this process can be accomplished mechanically. vThese will be described in some of the later examples.

One of the simplest procedures is to spread the ore over a fine meshed screen and, after immersing the screen under water, form a film of amine upon the water surface and then bring the screen containing the ore layer up through this lilm and then reverse the process. This procedure involves all of the principles necessary in a mechanical process and has been used by us as an experimental means of determining the amounts. vof reagents necessary and the separations which can be obtained.

vOn the appendedl sheets of drawings we have illustrated the general mechanical method employed in the present process, together with one suitable form of apparatus by which the process can be practiced continuously.

In the drawings,

Figures 1 to 6 are a schematic showing of the new principles used in the present invention.

Figure '7 is a cross-sectional view of one type of apparatus for practicing Vthe present process continuously.

In order that the general procedure may be clearly understood, reference is 'directed to Figure-s 1 to 6. In Figure 1 we show a`100jmesh screen on which there is a relatively thin layer of the silica-containing ore to be separated. This screen is then immersed beneath the surface of a layer of water maintained in a vessel as shown in Figure 2. By this procedure all of the ore particles are contacted with water. Then a few drops of a high molecular weight primary amine suitably dissolved in alcohol areY placed on the water surface. 'I'he amine immediately spreads to form a thin lm not more than a few molecules thick. In Figure 3, the depth of the film has been greatly exaggerated. The screen containing the ore is then passed upwardly (in the direction of'the arrow, Fig. 3) through the water and through the amine film as shown in Figure v4. Finally, the screen is then lowered into the water again, care being taken to avoid agitation so that theamine film will reform on the upper surface of the water. This amine film now contains silica, the other ore values remaining on the screen. As a last step, the silica film is scraped from the surface of the water. The process can be repeated at this stage by reforming a fresh amine lm andrepeating the raising and lowering of the screen any desired number of times. Figure 5 shows the screen after it has been lowered with the amine film containing the silica oating on the surface of the water. In Figure 6 we have endeavored to illustrate our conception of how the present-l invention operates theoretically. In this figure we illustrate a water surface carrying a nlm of a. primary aliphatic amine of high molecular weight. The hydrophvlic portion of the amine, namely the amino group, extends into the surface of the water and the alkyl portion of the amine, n'ot being hydro- Aphylic, remains on the surface of the water.

In many respects this conception is analogous to what is believed to happen when oleic acid is filmed on a water layer. The carboxyl group of the oleic acid is thought to extend downwardly into the water and the alkyl portion of the acid is thought to remain on the surface of the water.

For the successful practise of the present in- Vention it is essential that the ore be passed from a water phase to and through an amine lm in such a manner that the ore particles first meet the amine at the interface between the lm and the water, in this way insuring that the ore par- .ticles lirst contact the hydrophylic groups in the amine. The process is not operative if the amine is added haphazardly to an aqueous slurry of the ore. No lm holding the silica can be obtained thereafter. It is essential, as stated, that the procedural steps which we have broadly outlined in the above description be followed.

We shall now give a number of examples'illustrating the present invention and comparing its results with previous procedures.

Example 1 33.739 grams of a phosphate ore were spread 'evenly upon an eight inch, one hundred mesh sieve. The area of the sieve was 34.27 square inches. The phosphate ore used had the following analysis: 15.25 P205, 20.96 CaO, and

The sieve was then immersed underV B. P. L. product.

by us to obtain -the to 43.78%` of the original sample. The analysis was as follows: S102 85.45%, Ca0 7.10%, and P2055.34%. It isevident `that the film had selectively retained the silica.

This process was repeated using 0.011 lb. of amine per ton of ore and 7.848 gm. retained in the film. This corresponds vto 23.28% of the original sample. The composition was as follows: S102 66.35%., CaO 16.90%, and P205 12.80%. The process was' repeated a third time and 2.756 gm. retained inthe lm. This corresponds to 8.16% of the original sample and had the following compositions: Si02 33.09%, Ca0'34.40%, and .P205 25.80%.

8.3.61 .grams remained upon the screen which corresponds to 24.78% of the Original sample. This had the following analysis: Si02 4.46%, CaO 51.00%,l and P205 37.30%.

Based upon these results the distributions were as follows: Si02 66.04% -in the first concentrate. 27.23% vin the second, 4.77% in the third, and 1.96% in the residue. concentrate, 17.91% in the second, 12.73% in the third, and 57.15% in the residue. 4P205 14.03% in the rst concentrate, 17.85% 12.67% in the third, and`55.45% in the residue. This means that the residue contained 55.45% of the original bone phosphate, or in other words,

in the second,

CaO 12.21% in the first i a 55.45% recovery .of phosphate as Jan 81.46%

If the residuey is combined with the lastfraction removed the analysis of the product is as follows: SiOz 11.57%, Ca0 46.89%, and P205 34.45%. This gives a phosphate recovery of68.12% as a 75.24% VB. P. L. product. It can be seen that these results are outstanding when the recovery and percent B. P. L. are compared. The amount of amine necessary by this method to obtain a 68.12% recovery as a 75.24% E. P. L. product is only 0.022 1b. per ton of sample and the amount necessary to obtain a 55.45% recovery as an 81.46% B. P. L. product is only 0.033 lb. per ton of ore.

In order to compare these results with the 1 usual froth flotation separation a sample of the ore was separated ,in a Denver type froth flota,- tion cell. 38.655 grams were placed in a flotation cell and the equivalent of one pound per ton of dodecylamine reagent added. a This resulted in a concentrate which weighed 22.606 grams and analyzed as follows: S102 88.75%, Ca0 6.00%,

f and P205 4.34%. Thetailings weighed 16.055

grams and analyzed as follows: S102 14.45%, CaO 44.60%, and P205 32.81%. This corresponds to a separation of 86.25% of the silica in the concen trate and 80.43% of the phosphorus in the tailings. Thephosphate recovery is, therefore, 80.43% of a product` which contained 71.65% B. P. L.

It will be noted that.this `separation is not as selective as the former although they are comparable.

Approximately fifty times as much.

amine -was required for the froth flotation as in the 'process of the present invention.

In order to furtherfshow the effectiveness of this method as compared tothe usual flotation practice a sample of ore wastreated in the Denver type cell with the equivalent of 0.033 lb. per ton of dodecyl amine separation of Example v1.

lwhich is-the amount used This amountproved insufficient to produce any separation by froth flotation.

Example 2 v A 43.143 gram sample of the vsame ore used in Example 1 was treated by the procedure used in Example 1 using 0.033 gram of octadecyl amine per ton of ore. This resulted in the re# tardation in the yfilm of 18.892 grams (50.89%

of the-original) which analyzed as follows: Si02 87.21%, CaO 6.20%, and P205 4.65%. .An amount of amine equivalent to 0.011 lb. per ton was then added and `4.878 grains (13.07% of the original) was retained. This analyzed as follows: Si02 64.84%, CaO 18.80%, and P205 14.11%. The residue weighed 13.373 grams and had the following analysis: SiOz 9.75%, Ca0 48.58%, and P205 35.57%. The distribution of 'the ore values was,

l, vamount necessary by froth flotation processes.

Example 3 Using another sample of the ore described under Example 1 and a similar procedure the addition of an amount of d:decyl amine equivalent to 0.0030 1b. per ton of ore produced 54.28% of a residue which analyzed as follows: Si02 31.34%, CaO 37.65%, and P205 27.70%. The concentrate analyzed as follows: S102 89.45%, CaO 5.55%, and P202 4.24%. The amount of reagent used in this case\ is approximately oneA threeLhundredth of the amount required in froth flotation.

Example 4 33.106 grams of the phosphate ore described in Example 1 was treated with a total of 0.036`lb. per ton of dodecyl amine acetate in four portions using 0.009 lb. per ton of amine in each treatment. This resulted in a concentrate `which weighed 16.215 grams and had the following analysis: S102 93.36%, CaO 3.62%, and P205 24.81%. The 'residue weighed 16.891 grams and analyzed as follows: Si02 24.77%, CaO 41.60% and P205 30.00%.

' I Example 5 v48.901 grams'of an ore which analyzed 76.72% CaCOs and 15.07% Si02 wasspread out upon the screen and treated with, 0.009 gram of dodecyl amine as described under Example l. This resulted in a concentrate which weighed 10.121 grams and analyzed as follows: Si02 62.01% and CaCO: 34.27%. The residue weighed 38.780 grams and contained 87.79% CaCOa, Si02: The distribution of the silica and calcium lcarbonateis, therefore, as follows: 82.91% of the silica is present in the vconcentrate and 17.09% is in the residue, 90.73% of the calcium carbonate is in the residue and 9.27% in the concentrate.4

For comparative purposes a sample of the same" ore was separated' in a Denver type flotation cell using dodecylI amine as -the flotation agent. 49.781 grams were placed in the flotation cell and the equivalent of one pound per ton ot dodecyl amine added. This resulted in a concentrate-which weighed 13.370 grams andhadthe following analysis: S102 53.76% and CaCO:

and 3.34%

per ton of ore.

41.51%. The tailings weighed 36.411 grams and contained 5.36% silica and 85.15% calcium carbonate. The distribution of the ore values was, therefore, as follows: silica 26.02% inthe tailing and 73.98% in the concentrate, calcium carbonate 82.52% in the tailing and 17.48% in the concentrate.

It will be noted that the froth flotation requires over one hundred times as much reagent as that required in the process of the present invention.

Example 6 repeated. The solids in the film weighed 13.012 gra-ms and containing'60.23% silica and 31.02% calcium fluoride. The residue weighed 34.070 grams and contained 1.89% silica and 94.31% calcium fluoride. The distribution was, therefore, as follows: CaFg 88.84% in the residue 'and 11.16% in the concentrate, SiOz 7.57 in the residue and 92.43% in the concentrate.

A similar sample was separated in the Denver type flotation cell using octadecyl amine as the The lm containing the suspended solid particles was then collected and the process sulfate (calculated as barium oxide) and 22.91%

flotation agent. Using the equivalent of 1.75 lbs.

per ton of reagent 72.01% of the fluorite was recovered from the concentrate and 81.73% of the silica was present in the tailings.

It; will be Vnoted that the froth flotation was not as selective as the present process. The amount of reagent required presents a decided contrast, 0.018 lb. per ton in the case of the proposed process and 1.75 lbs. `per ton for the froth flotation. It is quite interesting to note tha-t' in the case of the froth otation using octadecyl amine as the flotation agent the calcium uoride oated away from the silica while in the present process the silica was retained in the film and the calcium uoride was formed in the residue. The present process differs from the usual processes employed not only in that it requires only a small percentage of the reagent formerly required but also reverses the flotation phenomena as regard the ore values oated. This is a fundamental difference between the two processes. In all cases observed using this process `the silicav has been retained by the film and the other ore values pass through it.

Example 7 51.734grams of a sample of galeria containing silica as the gangue mineral was placed-in the Denver type flotation cell and dodecyl amine added as the otation agent. The amount of amine necessary was the equivalent of 0.25 lb. This resulted in a concentrate which weighed 24.398 grams and which contained 82.2% leadand 4.24% silica. Thetailingsweighed 27.336 grams and contained 12.7% lead and 83.0% silica. This corresponds to a separation of 85.19% of the lead in the con- Y centrate and 95.64% of the silica in the tailings.

A sample `of the same ore was placed in a amine was then formed on the surface and the ore passed up through this film and then down again below the water surface. The amount of amine present corresponded to 0.01 lb. per ton of ore. The film, containing the entrapped solids, was lthen removed and the process repeated using a similar amount of dodecyl. amine. The total amount of amine used was, therefore, the equivalent of 0.02 lb. per ton of ore. 93.21% of the silica originally present was removed by the film and 83.22% of the lead was present in the residue.

These results are significant in view of the fact that in a flotation cell or by other processes galena is easily floated from silica and as a rule the separation does not require a large amount of reagent. In this example the silica is retained by the lm and the galena rejected. The amount' of reagent necessary is only a small proportion of that required by other process.

Example 8 17.801 grams of a barite ore were spread evenly'over the surface of a two hundred mesh screen. The ore contained 46.82% barium grams and contained 61.00% barium sulfate (calculated as barium oxide) and 5.38% silica.

The distribution of the ore values is, therefore, as follows: BaO 22.76% in the first suspension, 12.43% in the second suspension, and 64.81% in the residue, SiOz 71.98% in the rst suspension, 16.33% in the second suspension, and 11.69% inthe residue.

. 'I'hese results are economically striking since a satisfactory separation has been obtained with the use of a total amount of dodecyl amine equivalent to 0.044 lb. per ton of ore. Comparative results using the Denver type flotation cell required 1.5 lbs. per ton of ore to effect a separation. In the case of the froth flotation procedure it is the barium sulfate which is preferentially floated.

In Figure 7 we have illustrated in a schematic Way suitable apparatus for practicing the principles ofthe present process continuously.`

In this fig-ure, a long, narrow trough l0 contains water through which a belt l2 is drawn over a series of idlers' and pulleys. The ore to be separated is charged in hopper l5 from which it feeds onto the belt I2 continuously moving in the direction of the arrow. This belt carrying the ore is then caused to pass under the pulley I3 over vidler I4 and up through a segregated zone of the water surface which has been supplied with the amine. A bottomless boxlike, rectangular barrier I6 is arranged in tlzewater to close off a rectangular area thereof and at thesurface of the water. By means of container Il and discharge nozzle 18 the primary amine is supplied to the water surface and remains as a film of restricted area maintained within the confines of the barrier. The water surface is indicated by the dotted line I9 and the lm is maintained on this surface. In' consequence, as the ore on the belt passes over and under the gidlers I4 and 2| adjacent barrier I6, the ore is first wetted with water and' then passed upwardly through the amine film. The belt is then caused to pass over the next set of idler pulleys, 22 and 23, to the left of barrier vI6 and then downwardly through a barrier arrangement 24 where the film of amine is reformed on the surface of the Water from which it can be skimmed off in any convenient manner at point 25. This represents a complete cycle of the separation, and the cycle can lbe repeated any number of times. In Figure 7 We have shown three repeti-V tions of the cycle. Thus, as shown in the drawings, the belt continues its travel under pulley 26 through another barrier 21' supplied with amine from container 28 over and under idlerl pulleys 29 and 30 where the `iilm is disrupted and coats the 'ore particles, thence to barrier arrangement 3l where the lm is reformed and the nlm skimmed off at 32 and so on through the films maintained in barriers 33 and 34, and the films containing solid particles reformed in barriers '36 and 31 from which the film is skimmed off at 3and 39. Pulleys and idlers for guiding the belt through barriers 3l, 33, 34,

3B and 3l are shown at 40, 4|, 42, 43, 44, 45, 46,l

V4l, 4B, -49, 50, 5| and`52. Discharge containers for the amine areshown at A53 and 54. Finally, the belt passes over drum 55 and the ore, re-

of silica from calcium phosphate ores, the very small amount ,of gangue, retained in the film is such that the process is notV satisfactory .com-

mercially.

In our process it is not necessary to deslime or otherwise treat the ore before it is subjected to our type of separation. O ur results indicate that the separation is as satisfactory with `an undeslimed as with a completely deslimed ore and Vthat no greater amount of reagent in the lm'is required in the former case. This is, of

y course, quite advantageousfroma commercial standpoint since the process of deslimng is quite often costly in itself and often leads to substantial losses of desirable ore values. Y

`Having thus-described our invention, what we claim is:

1. The process of separating silica from ores containing the same which includes providing a lm of a substantially water-insoluble primary aliphatic amine on a layer of water beneath which the ore to be separated is disposed, passing the ore to and through the film, and then submerging the ore beneath the water surfaceto reform the lm on the water surface whereby silica in the ore is preferentially retained in the reformed film.

2. The process of separating silica from ores containing the same which includes passing the Y ore beneath the surface of a pool of water, formmaining thereon scraped off by scraper 56 from whence it falls to the discharge .opening 51 in the housing 58. Drums 55 and 59 over which the` belt passes can be driven by any suity able means, not shown.

Thus the process can be rendered. continuous by continuously charging ore to be separated on the Ibe1t,.passing the -belt through layers of amine film, then reforming the lm, skimming off the film for the recovery of silica therein, and finally recovering the ore remaining on the belt. Itis understood that Figure 7 and the description thereof is not intended to be a descrip'- tion of all of the necessary mechanical parts for the operation of the belt conveyor but is simply intended to illustrate an alternative method by which We can vpractice the principles of the present invention. p

In the preceding examples we have shownthat ores may be separatedl by passing themup through an adsorbed nlm, which process serves torupture 4the film, and that the film can be reformed by passing the ore under the water surface. This second process serves to refonn the 111m. We have shown that certain ore valuesk lare retained by the film and others pass through the nlm and under the water surface. Allthe primary amines we use are insoluble, or substantially insoluble, in water. Thus we are limited to primary amines having at leastslx carbon atoms and these range from hexyl amine to octadecyl amine 4and the unsaturated primary amines of like number of carbon atoms.

ing a film of a substantially water-insoluble primary aliphatic vamine on the water surface, passing the ore to and through the amine nlm, and then submerging the ore beneath the water surface to reform the lm on the water where'- by the silica Ain the ore is preferentially retained in the reformed film.

3. The process of separating silica from ores containing the same which includes charging the ore. on a continuously moving belt, passing the ore on the belt intofa trough of water, passv ing the wetted ore on the belt upwardly through a lmof a substantially water-insoluble primary aliphatic amine of restricted area4 maintained on said trough of water, passing the ore on said belt downwardly through another portion of said water trough to reform said film,

the lm containing silica, and removing the lm `from the water surface.

4. The process as in claim 1 wherein the ore Avis a phosphate ore.

as m claim 2 wherein the as in' claim 3 wherein the l ore is a phosphate ore and the amine is dodecyl.

" Films of mineral oils, etc., are rather dimcult l to form and our experimental work has shown them to-be of no value whatever for this purpose. Likewise. nlms of oleic acid are not at all suited to the present process. Although oleic `11. The process vas in claim v2 wherein the ore is phosphate ore and the amine is dodecyl.

` j 12. The process as in claim 3 wherein the l ore is a phosphate ore and the amine is dodecyl.

ANDERSON W. RALs'roN. ERVINY'W. SEGEBRECHT.

acid will suspend-and collect a small-amount l 

